Guest pokey Posted July 8, 2007 Posted July 8, 2007 This little "demonstration/test" is about pilotage & common sense. (& the difference) Here is the scenerio: Day one there is no wind & we take 200 mile round trip/cross country (100 miles each way) & fly @ 100 mph. Day two there is a 50 mph headwind on way there & 50 mph tailwind on way back & we take same route & fly same speed as yesterday. how much time will it take us to complete the 200 mile trip on both days ? Quote
palmfish Posted July 8, 2007 Posted July 8, 2007 This little "demonstration/test" is about pilotage & common sense. (& the difference) Here is the scenerio: Day one there is no wind & we take 200 mile round trip/cross country (100 miles each way) & fly @ 100 mph. Day two there is a 50 mph headwind on way there & 50 mph tailwind on way back & we take same route & fly same speed as yesterday. how much time will it take us to complete the 200 mile trip on both days ? Well, not counting approach/departure time, enroute delays, etc... 2:00 on the first day. 2:40 on the second day. Quote
RockyMountainPilot Posted July 8, 2007 Posted July 8, 2007 (edited) This little "demonstration/test" is about pilotage & common sense. (& the difference) Here is the scenerio: Day one there is no wind & we take 200 mile round trip/cross country (100 miles each way) & fly @ 100 mph. Day two there is a 50 mph headwind on way there & 50 mph tailwind on way back & we take same route & fly same speed as yesterday. how much time will it take us to complete the 200 mile trip on both days ? 2.0 & 2.66 Respectively. Is this a trick question? Edited July 8, 2007 by RockyMountainPilot Quote
Guest pokey Posted July 8, 2007 Posted July 8, 2007 2.0 & 2.66 Respectively. Is this a trick question? not at all, but i should have pointed out that it was aimed at 'student pilots' and i think you used you pencil to do the math ! Quote
RockyMountainPilot Posted July 8, 2007 Posted July 8, 2007 not at all, but i should have pointed out that it was aimed at 'student pilots' and i think you used you pencil to do the math ! No pencil used. And why would this be any harder for a student pilot? Am I missing something? Quote
Guest pokey Posted July 8, 2007 Posted July 8, 2007 No pencil used. And why would this be any harder for a student pilot? Am I missing something? either you are or i am Quote
Goldy Posted July 8, 2007 Posted July 8, 2007 (edited) either you are or i am WOW, I dont think a pencil is really necessary, is it ? I could do it faster in an R 44. ( 150MPH ship) Is that the right answer? I'll go back and study for my instrument now. Goldy Edited July 8, 2007 by Goldy Quote
Linc Posted July 8, 2007 Posted July 8, 2007 When do we get out of the car and start flying in aircraft? (mph vs. knots) Quote
Whistlerpilot Posted July 9, 2007 Posted July 9, 2007 Hi, a student pilot here. Assuming 100 mph IAS don't both days trips take the same time of 2 hours? Quote
FUSE Posted July 9, 2007 Posted July 9, 2007 Hi, a student pilot here. Assuming 100 mph IAS don't both days trips take the same time of 2 hours? No, if your KIAS is 100 your groundspeed will change with the wind speed. If there is no wind at all then your ground speed will match your KIAS. But lets say you have a 50 knot headwind. If your KIAS is 100 your GS will only be 50 kts. So it will take you about twice as long to cover the same distance. But if you have a 50 knot tailwind and your KIAS is 100 your GS will be 150kts, so now your cover the same distance faster. I believe that the answer is 2 hours with no wind and 2.4 hours with the wind variables but I sort of don't understand. I would think that with the wind it would be 2.5 hours... Do I have that right guys????? and Pokey, thanks for the question, I wish we could have more of them on here, I love em.... Quote
Guest pokey Posted July 9, 2007 Posted July 9, 2007 (edited) Hi, a student pilot here. Assuming 100 mph IAS don't both days trips take the same time of 2 hours? read Fuse's reply. But your answer is one of the ones i was looking for. One may initially think that the headwind would cancel out the tailwind, since they are both the same, but not so. Reminds me of the ships: "if it takes 1 ship 30 days to sail to England, then it should take 30 ships 1 day" (looks good on paper) No, if your KIAS is 100 your groundspeed will change with the wind speed. If there is no wind at all then your ground speed will match your KIAS. But lets say you have a 50 knot headwind. If your KIAS is 100 your GS will only be 50 kts. So it will take you about twice as long to cover the same distance. But if you have a 50 knot tailwind and your KIAS is 100 your GS will be 150kts, so now your cover the same distance faster. I believe that the answer is 2 hours with no wind and 2.4 hours with the wind variables but I sort of don't understand. I would think that with the wind it would be 2.5 hours... Do I have that right guys????? and Pokey, thanks for the question, I wish we could have more of them on here, I love em.... You are correct Fuse, do the math tho: 100 divided by 150= 2/3 OR 40 minutes I like question/answer session too,,, we need MORE of it, i agree ! (keeps the peanut gallery awake too) Oh, & by the way Linc? alot of aircraft flying around these days still use the statute mile on their airspeed indicaters, some even have BOTH scales. THAT may be another good question for student pilots?------------- What is the difference bewtween a knot & a mph? How can we prove it & what is the conversion factor? Edited July 9, 2007 by pokey Quote
Goldy Posted July 10, 2007 Posted July 10, 2007 (edited) What is the difference bewtween a knot & a mph? How can we prove it & what is the conversion factor? Knots are more fun ! Difference is obvious. Travel time over a nautical mile versus a standard mile. And the conversion is a short 1.15 Now, what is the speed of sound? And if you can tell me an answer without asking one more question, YOURE WRONG ! I love this stuff. Goldy Edited July 10, 2007 by Goldy Quote
joker Posted July 10, 2007 Posted July 10, 2007 (edited) And if you can tell me an answer without asking one more question, YOURE WRONG !Through what medium do you want the speed of sound? If I remember my primary school mathematics correctly,the speed of sound in air at 0 oC and absolute pressure 1 bar can be calculated as c = (k p / ρ)1/2 = (k R T)1/2 (3) where k = ratio of specific heats (adiabatic index) p = pressure (Pa, psi) R = gas constant T = absolute temperature (oK, oR) For Example: c = (1.4 287 273)1/2 = 331.2 (m/s) where k = 1.4 and R = 287 (J/K kg) and in water: c = (2.06 109/999.8)1/2 = 1435.4 (m/s) where Ev= 2.06 109 (N/m2) and Ï = 999.8 (kg/m3) Joker Edited July 10, 2007 by joker Quote
Guest pokey Posted July 10, 2007 Posted July 10, 2007 Knots are more fun ! Difference is obvious. Travel time over a nautical mile versus a standard mile. And the conversion is a short 1.15 Now, what is the speed of sound? And if you can tell me an answer without asking one more question, YOURE WRONG ! I love this stuff. Goldy fun knots ! -YIP ! ( 'cept if they in yer panties OR shoe laces) Is anything ever obvious? see Joker's 'splanation for speed of sound the answer to 1 question, usually leads to MORE questions Through what medium do you want the speed of sound? Ï = 999.8 (kg/m3)Joker [/indent] how about thru one ear & out the other? & Joker? i am still checking yer kalkalashuns,,, will get back to ya in a week or so K? OK, my head hurts now..... i know the feeeling,,,,,,,,,,,,,,,,,, Quote
PhotoFlyer Posted July 10, 2007 Posted July 10, 2007 Who can tell me the history of the term knots? The conversion factor is 1.15, but how many feet is a statute mile? A nautical mile? Quote
kodoz Posted July 10, 2007 Posted July 10, 2007 Who can tell me the history of the term knots? The conversion factor is 1.15, but how many feet is a statute mile? A nautical mile? I think one possible origin is that evenly spaced knots in a rope affixed to a stationary object were used when measuring a ship's speed--sailors counted the number of knots per time to get their speed. to covert, take (5280 ft/1 SM) x (1.15 SM/1 NM) = 6072 feet in a NM --c Quote
joker Posted July 10, 2007 Posted July 10, 2007 (edited) Yes, the rope was attached to a peice of wood called a 'chip-log', which was thrown overboard. Then as the ship sailed away, the knots (which were tied at intervals) were counted over a period of time (measured by a sandglass), and reported to the officer of the watch. Interestingly, today we still call the 'speedometer' on a sailing boat a 'log'. Maritime history is facinating. There are so many relics of the past that are still in common use today. Joker P.S. As I have managed to successfully steer this thread to include one of my other passions (sailing) I share with you this website, which is all about knots! It's one of my favourites. Just a little extra! Animated Knots Edited July 10, 2007 by joker Quote
Goldy Posted July 11, 2007 Posted July 11, 2007 Through what medium do you want the speed of sound? If I remember my primary school mathematics correctly,the speed of sound in air at 0 oC and absolute pressure 1 bar can be calculated as c = (k p / ρ)1/2 = (k R T)1/2 (3) where k = ratio of specific heats (adiabatic index) p = pressure (Pa, psi) R = gas constant T = absolute temperature (oK, oR) For Example:c = (1.4 287 273)1/2 = 331.2 (m/s) where k = 1.4 and R = 287 (J/K kg) and in water:c = (2.06 109/999.8)1/2 = 1435.4 (m/s) where Ev= 2.06 109 (N/m2) and Ï = 999.8 (kg/m3)Joker Holy Cow Joker ! I was just looking for someone to acknowledge that the speed of sound changes with altitude ! Goldy Quote
joker Posted July 11, 2007 Posted July 11, 2007 (edited) Goldy, Here is a link to a java air density simulator. Air density simulator I found this simple explanation on the web! Joker Hewitt, P.G. Conceptual Physics, fourth edition, copyright 1981. "The speed of sound depends on wind conditions, temperature, and humidity.It does not depend on the frequency of sound; all notes travel at the samespeed. The speed of sound in dry air at 0 degrees C is about 330 meters persecond, nearly 1,200 kilometers per hour. Water vapor in the air increasesthis speed slightly. Sound travels faster through warm air than throughcold air. This is to be expected because the faster-moving molecules inwarm air bump into each other more often and therefore transmit a pulse inless time. For each degree rise in temperature above 0 degrees C, the speedof sound in air increases by 0.6 meters per second. In water, sound travelsabout four times as fast as it does in air, while in steel, the speed ofsound is about fifteen times as great as in air." Edited July 11, 2007 by joker Quote
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